Present packaging techniques for electrically isolating semiconductor dies from the package itself or other semiconductor dies included in the package is typically obtained via brazing or soldering ceramics, such as beryllium oxide, aluminum oxide, and so forth, first to predetermined locations on the surface of the main mounting pad of the associated package, and thereafter brazing or soldering the appropriate semiconductor dies to the soldering ceramics so deposited on the main mounting pad. Such an isolation method is expensive, due to the relatively high cost of ceramics, and the additional labor cost in first attaching the ceramics to the mounting pad, and thereafter the semiconductor dies to the ceramic so deposited.
There are many different packaging configurations and methods for mounting semiconductor devices, such as integrated circuits and/or semiconductor dies. Eight of these prior methods and mounting assemblies for packaging semiconductor dies are discussed in the following paragraphs.
Simmons U.S. Pat. No. 3,569,797 teaches a mounting assembly for a semiconductor device for electrically isolating the die from the housing, which housing is filled with a thermal conducting filler to provide for a good thermal conductivity between the electrically isolated die and the housing. The encapsulated lead frame 17 includes leads 19, 20, and 21. These leads each are rigidly connected at one end to a mounting tab 18. The other end of one of the leads, namely lead 20 terminates in a rectangular-like mounting platform 25 at its other end for receiving a semiconductor die. The other ends of leads 19 and 21 have lateral extending portions 26 and 27, respectively, terminating at riser sections 28 and 29, the other ends of the latter terminating to sections 30 and 31, respectively having inwardly extending arms 32 and 33, respectively, which are formed to provide spring pressure on the top of a die for forcing the same against the platform 25.
Lincoln, U.S. Pat. No. 3,893,158 discloses in FIG. 10 a lead frame 130 including centrally located extensions of the leads for providing mounting surfaces for dies 132, 134 and 136. Similar lead extensions terminating in mounting pads for dies are shown in other of the figures of this patent. Wire bonding is used to connect wires between the dies and various ones of the contact fingers. The lead frame assembly is epoxy encapsulated within the housing. Note that the dies are electrically isolated from one another relative to their mounting, but are oriented for permitting a light emitting die to transmit light to a light detecting die.
Bliven et al U.S. Pat. No. 4,003,544 shows in FIG. 1 a lead frame including extensions of contact fingers for providing centrally located mounting pads for integrated circuit chips or dies. The particular configuration is designed to facilitate the plastic encapsulation of the lead frame and die assembly.
King U.S. Pat. No. 4,114,177 teaches an optically coupled device including a lead frame having leads with extensions into the central portion of the frame, with landing pads or mounting pads at the ends of the lead extensions for receiving a photo detector integrated circuit die on one pad, and a light emitting integrated circuit on an opposing pad from a lead on the opposite side of the lead frame.
Aird U.S. Pat. No. 4,446,375 discloses a lead frame for receiving the integrated circuit dies associated with an optical coupler. The dies are mounted on pads that are centrally located, with each pad being provided via extensions of leads of the lead frame. Other than centrally located lead extensions serving as mounting pads for integrated circuit dies.
Meddles U.S. Pat. No. 4,556,896 teaches a lead frame structure for a semiconductor device. The structure includes centrally located mounting pads as extensions of leads for mounting integrated circuit dies. The lead elements are arranged to facilitate the molding of a housing about the lead frame assembly.
Ching et al U.S. Pat. No. 4,633,582 discloses a lead frame assembly that includes centrally located mounting tabs as extensions of lead fingers of the lead frame, upon which integrated circuit dies are mounted. The lead frame design is intended to insure a coplanar relationship between first and second lead assemblies of the overall lead frame, as the same as rotated from one position to another during manufacturing of the optoisolator device associated with the lead frame.
Hawkins U.S. Pat. No. 4,740,868 discloses a lead frame that includes a plurality of rails upon which a plurality of integrated circuit dies can be mounted. In addition to providing mounting surfaces, the rails also function as heat sinks. The rails are laid out in a manner for providing electrical isolation between rails.